We propose using established longitudinal studies of 7300 parents and twin children to investigate how gene environment interplay influences the development of substance abuse (SA). Our focus is on children assessed repeatedly, beginning in pre-adolescence at age 11 and then again at approximately ages 14, 17, 20, 24, and 29, making it possible to examine the development of individual differences within narrowly defined age ranges that correspond roughly to key life transitions associated with important changes in environmental context (starting high school, leaving the parental home, exposure to new peers, etc). Our studies involve representative, community based samples with high participation rates, and thorough age appropriate, psychometrically sound assessments covering 1) substance use, misuse, and dependence;2) disorders, personality traits, and behaviors related to behavioral disinhibition;3) psychophysiogical endophenotypes for SA risk;and 4) environmental adversity derived from multiple domains (family relationships, trauma, peer group quality, exposure to substances, etc.) over multiple developmental stages. We propose obtaining blood-based DMA from approximately 5000 study participants which, along with deidentified personal data, will be added to the NIDA Genetics Consortium (NGC) public repository. We will obtain consent to participate in this GEDI initiative from an additional 2300 individuals whose data will already be part of the NGC. We will carry out a 2-stage genome wide association study using a 1M SNP bead array with 1000 parents followed by confirmation genotyping with an additional 2700 parents using three SA related latent phenotypes focused on a) SA risk, b) behavioral disinhibition attributes, and c) brain electrophysiology (event related potentials and oscillations). These three quantitative phenotypes will be developed and refined early in the funding period so as to capture complementary aspects of genetic risk for SA similarly in parents and young adult offspring. Offspring (N=3582) will then be genotyped using candidate genes identified in the parent study as well as in the evolving SA literature. A composite measure of environmental adversity will also be developed and used in hypothesis driven tests of GxE effects in offspring that include examination of the developmental specificity of effects and their replicability across related measures, developmental time points, and offspring samples. Also included will be hypothesis-generating exploratory analyses that take advantage of the richness of the phenotypic data available from our families and the rapid pace of development in molecular biology and statistical genetics.